The question (15 marks)
Why is the converse of an A proposition a particular proposition, and why has an O proposition no converse at all? Explain, with the aid of the table of eductions, why an I proposition has no contrapositive and why only universal propositions have an inverse. (15 marks)
MU Module III, head 3.3; pack ch. 10 and 11.
Plan your answer on paper before you look at the authorities — issue first, then the rule, then apply it to these facts.
It tests Unit 3 · Inference of Logic – I.
Authorities you will need
- Aristotle, whose rules of conversion these are as transmitted by the traditional logicians
- Keynes, Formal Logic, whose scheme of seven eductions is followed
- Bain, who adds material obversion to the list of immediate inferences
How an answer is marked
A full-marks answer names the issue in one line, states the rule with its section, cites the authority, applies it to these facts and concludes — in that order. The app's model answer for this question is written in exactly that shape, with a checklist to mark your own attempt against.